The invention relates to an aspirator for use in conjunction with an engine fan shroud to provide a vacuum.
Engine air intake systems have typically included a scoop, precleaner, ducts of varying lengths, and an air cleaner. Such a precleaner requires a vacuum to pull or "scavenge" small dirt particles out of the fresh air ingested into the air intake system inlet or scoop. Exhaust system aspirators have been used to supply the required vacuum. But an exhaust system aspirator will create a restriction in the engine exhaust, raise noise levels and raise the cost of the muffler and/or the exhaust pipe. Also, a check valve is needed to prevent backflow of high temperature gasses into the precleaner and high temperature hoses must be used.
Some production vehicles have used a fan shroud aspirator as a source of vacuum to a precleaner which scavenges dirt from their cab air intake system. This aspirator is merely an opening in the shroud enabling a hose to link with the precleaner. With this type of fan shroud aspirator certain conditions also create back flow into the precleaner, therefore dirt particles are not removed from the air. Accordingly, it would be desirable to have a precleaner aspirator which avoids the disadvantages associated with the aforementioned aspirators.